Muskie vs. Northern pike
Minnesota's muskie apparently have evolved to avoid head-on competition with northern pike. If northern pike find their way into muskie water, they seem to proliferate at the expense of muskies.
Why does the northern pike compete better? That question continues to puzzle fish biologist, though many believe that the earlier-hatching northern pike prey on newly hatched muskie if the two species use the same spawning areas.
In waters where muskie evolved without northern pike present - such as the Park Rapids area lakes, Shoepack Lake and much of Wisconsin - the muskie chooses the same weedy, flooded wetlands that serve as northern pike spawning areas elsewhere. If pike are introduced to these lakes, as they have been in Wisconsin drainages, the northern pike spawn in these same areas - but about two weeks earlier. So when the muskie fry hatch, they may be eaten by the larger young-of-the-year northern pike.
To make matters worse, young muskie routinely hang just below the surface of the water, where they are easy prey for birds from above or fish from below. Where the two species have coexisted for thousands of years, as they have in the Mississippi River headwaters, the muskie seem to have adopted different spawning areas. In Leech Lake, for example, muskie spawn offshore in 3 to 6 feet of water. Northern pike, meanwhile, use the weedy shorelines of bays and presumably have less chance to prey on the muskie.
Other evidence suggests that riverine conditions help muskie hold their own against northern pike, which prefer slower, weedier water. Indeed, among the areas in Minnesota where muskie and northern pike coexist are the Rainy, Big Fork, Little Fork, St. Croix and Mississippi rivers. Researchers have speculated but haven't proved that northern pike-muskie competition may be affected by other factors, including disease, dissolved oxygen concentrations, water-temperature fluctuations at spawning time, and prevailing water temperatures.